Tweet, Screech, Hey: Animal Sounds Hint at Evolution of Language

Tweet, Screech, Hey: Animal Sounds Hint at Evolution of Language

With its complex interweaving of symbols, structure, and meaning, human language stands apart from other forms of animal communication. But where did it come from? A new paper suggests that researchers look to bird songs and monkey calls to understand how human language might have evolved from simpler, pre-existing abilities.

One reason that human language is so unique is that it has two layers, says Shigeru Miyagawa, a linguist at the Massachusetts Institute of Technology (MIT) in Cambridge. First, there are the words we use, which Miyagawa calls the lexical structure. “Mango,” “Amanda,” and “eat” are all components of the lexical structure. The rules governing how we put those words together make up the second layer, which Miyagawa calls the expression structure. Take these three sentences: “Amanda eats the mango,” “Eat the mango, Amanda,” and “Did Amanda eat the mango?” Their lexical structure — the words they use — is essentially identical. What gives the sentences different meanings is the variation in their expression structure, or the different ways those words fit together.

The more Miyagawa studied the distinction between lexical structure and expression structure, “the more I started to think, ‘Gee, these two systems are really fundamentally different,’ ” he says. “They almost seem like two different systems that just happen to be put together,” perhaps through evolution.

One preliminary test of his hypothesis, Miyagawa knew, would be to show that the two systems exist separately in nature. So he started studying the many ways that animals communicate, looking for examples of lexical or expressive structures.